1. Field of the Invention
The present invention relates to otic prosthesis in general and in particular to a middle ear prosthesis used in both complete and partial ossicular repair.
2. Description of the Prior Art
It is presently known to repair the sound conducting mechanism of the middle ear by surgical implantation of various types of prosthesis. Such repair may involve either complete or partial reconstruction replacement of all three ossicles between the tympanic membrane of the outer ear and the oval window of the inner ear.
The three ossicles include the malleus, the incus, and the stapes. When only the malleus and the incus are removed with the stapes being left intact, the prosthesis need span only the space between the tympanic membrane and the superstructures of the stapes, mainly the capitulum (stapes head). This is generally referred to as a partial ossicular reconstruction procedure. When the stapes superstructures are removed along with the malleus and incus the prosthesis spans the entire space between the tympanic membrane and the stapes footplate and is generally referred to as a complete ossicular reconstruction procedure.
Known prior art prosthesis for both complete and partial reconstruction procedures have been made from various natural materials such as cartilage and bone, and from various man-made materials such as stainless steel and plastics like Teflon, Polyethelene, and biocompatible materials like Proplast and Plastipore. New ceramics are also being developed.
Irrespective of the material the prosthetic devices known are usually one piece straight shaft devices having a head portion resting against the tympanic membrane with the opposite end pressing against the footplate of the stapes in complete reconstruction procedures or the stapes capitulum-superstructure in partial reconstruction procedures.
For a discussion of prior art prosthetic devices and the implanting techniques of same, the reader is referred to the following articles which discuss such devices in greater detail. These articles are "A DECADE OF TYMPANOPLASTY: PROGRESS OR REGRESS?" by David F. Austin, M.D. appearing in the May 1982 Issue of Larynogoscope 92: "BIO COMPATIBLE OSSICULAR IMPLANTS" by John J. Shea, M.D. and John R. Emmett, M.D. appearing in Volume 104, April 1978, Issue of Arch. Otolaryngol. and "OSSICULAR CHAIN RECONSTRUCTION: THE TORP AND PORP AND CHRONIC EAR DISEASE" by C. Gary Jackson, M.D. et.al. appearing in the Aug. 1983 Issue of Larynogoscope.
Wire prosthetic devices are also known. However, such devices consist of a straight shaft stainless steel wire with a transverse bar located at one end of the wire shaft. The bar or any other transverse section is intended to limit the insertion of the device into any base material located under the tympanic membrane. All straight shaft prosthetic devices give rise to certain problems due to their lack of flexibility such as a slight outward retraction and/or shift of the tympanic membrane which may occur during the post-operative healing process. This outward retraction causes the tip of the prosthetic device to lift off from either the footplate or stapes head, depending upon the type of reconstruction, resulting in a loss of the tension pressure between the tympanic membrane and the footplate that was initially set by the surgeon implanting the prosthetic device. Thus the patient does not hear as well after the healing from the operation as he did when the operation was just performed. In situations where the ear is subjected to a loud noise, the extreme deflection of the tympanic membrane caused by the noise may damage the inner ear--the cochlea. Also, there is no protection for inner ear damage from external physical trauma to the ear.
Thus it is seen that a prosthetic device is required which would provide flexibility to absorb shocks induced by loud noises or other external trauma to the ear and which would have sufficient flexibility to compensate for any displacement change between the tympanic membrane and the inner ear due to outward retraction and/or shift occurring during the post operative healing process to maintain sufficient pressure between them to insure adequate hearing restoration over an extended period of time.